Analysis of RefractoriesThermo Scientific ARL PERFORM’X Series Advanced X-Ray Fluorescence Spectrometers

IntroductionRefractories are, as defined by ASTM C7, non-metallicmaterials having chemical and physical propertiesallowing for applications in structures or as componentsof system that are exposed to environmental conditionsabove 1000�F (538�C). These materials are mainly used aslinings in furnaces, kilns, incinerators and reactors

To meet the requirement of extreme heat exposure,refractories are normally compositions of the oxideformed aluminum (alumina), silicon (silica), magnesium(magnesia) and zirconium (zirconia).

The main elements must be monitored in theproduction of the refractories to insure propercomposition for the desired application. Many minor andtrace elements must also be monitored in the refractoriesto insure optimal stability and reduce potentialcontamination issues for their customer.

Refractories are highly stable oxide composition,making it very difficult to dissolve the samples forstandard wet chemical or flame AA/ ICP analysis. It is forthis reason that wavelength dispersive X-ray fluorescence(WDXRF) is an ideal instrument for daily routine processquality assurance and control along with advance researchand development.

WDXRF analysis is a stable fast analytical techniquewhich requires very little sample preparation. Samples inWDXRF simply can be analyzed as loose powder, pressedpellet, lithium borate fusion or even in a liquid solution.

Instrument

Thermo Scientific ARL PERFORM’X series spectrometerused in this analysis was a 4200 watt system. This systemis configured with 6 primary beam filters, 4 collimators,up to nine crystals, two detectors, helium purge and our5GN+ Rh X-ray tube for best performance from ultra-lightto heaviest elements thanks to its 50 micron Be window.This new X-ray tube fitted with a low current filamentensures an unequalled analytical stability month after month.

The ARL PERFORM'Xoffers the ultimate inperformance and sampleanalysis safety. Its uniqueLoadSafe design includes aseries of features thatprevent any trouble duringsample pumping andloading. Liquid cassetterecognition prevents anyliquid sample to be exposedto vacuum by mistake. Overexposure safety automaticallyejects a liquid sample if X-rayexposure time is too long.

The Secutainer system protects the primary chamberby vacuum collecting any loose powders in a speciallydesigned container, easily removed and cleaned by anyoperator. For spectral chamber protection, the ARLPERFORM'X uses a helium shutter designed for absoluteprotection of your goniometer during liquid analysisunder helium operation. In the "LoadSafe Ultra" optionalconfiguration, a special X-ray tube shield provides totalprotection against sample breakage or liquid cell rupture.

CalibrationAnalyzing the refractory samples accurately and preciselyrequires not only the detection of low X-ray intensities atthe trace elemental concentrations but also at very highconcentrations. For optimal analytical analysis, theconditions and parameter used in this measurement wereset to maximize the excitation of each element whilekeeping the background as low as possible.

A set of certified standards were used in the creationof elemental regression plots. Plots for Al, Ca, Si and Zrare shown in below graphs. These graphs are linearregression of the known concentration plotted against themeasured intensities. The linearity of these curves dependsupon the stability of the instrument, inter-elementalcorrection capabilities of the software, the accuracy of thestandard and the quality of the sample preparation.

Key Words

• ARL PERFORM’X 4200 W

• Refractories

• XRF

• X-ray fluorescence

ApplicationNote: 41663

ResultsThe calibration ranges are the dynamic range within thecalibration standards used for this report. These rangescan be increased by the addition of standards containingthe newly desired concentration. The standard deviations(SD) and relative standard deviations (RSD) are the typicaldeviation from the standard values achieve from the linearregression at 60 seconds counting times.

Calibration SD RSD LoD Elements Range (%) (%) (%) (%)

Al Kα� 0.08 - 100 0.0066 0.171 0.0051

Ca Kα� 0.04 - 100 0.0156 0.027 0.0004

Co Kα� 0.5 - 1.0 0.0001 0.333 0.0004

Cr Kα� 0.004 - 12 0.0002 1.053 0.0006

Fe Kα� 0.05 - 50 0.0018 0.036 0.0007

Hf Lb� 1.0 - 2.5 0.0004 0.432 0.0022

K Kα� 0.001 - 15 0.0006 0.126 0.0006

Mg Kα� 0.015 - 100 0.0061 0.252 0.0086

Mn Kα� 0.05 - 10 0.0006 0.288 0.0006

Na Kα� 0.01 - 8.0 0.0080 0.801 0.0196

P Kα� 0.03 - 12 0.0004 0.450 0.0010

S Kα� 0.4 - 3.0 0.0035 0.189 0.0030

Si Kα� 0.4 - 100 0.0154 0.072 0.0006

Ti Kα� 0.01 - 5.0 0.0005 0.468 0.0080

W Lα� 1.0 - 5.0 0.0005 0.531 0.0010

Y Kα� 0.5 - 1.0 0.0001 0.099 0.0001

Zr Lα� 0.03 - 100 0.0005 0.306 0.0018

Table 1: Typical results for refractories

Standardless analysis One of the most useful developments in the analyticalsoftware programs for XRF has been the availability of"standardless" or semi-quantitative packages. Thesepackages allow for quantitative data to be obtained forcomplete unknown samples.

Thermo Scientific UniQuant™ is a factory calibrationbased on 64 pure element standards that allows forconcentration determination of unknown samples in anymatrix by using complex mathematical algorithms for upto 79 elements. These algorithms correct for matrix effectsas well as inter-elemental effects to provide a highlyaccurate and precise quantitative results.

ConclusionThe results show that refractory analysis can easily beperformed with the ARL PERFORM’X sequential XRFspectrometer. The precision and accuracy are shown to beincredibly high in this matrix type. Of course the accuracyand precision can easily be increased by extended theelemental counting times. This would allow for muchbetter SD and %RSD at all concentration ranges.

Furthermore, operation is made easy through thenewest and most advance state-of-the-art ThermoScientific OXSAS WDXRF software which operates withthe latest Microsoft Windows® 7 packages.

To see our complete X-ray product portfolio, visitwww.thermoscientific.com/xray.

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Figure 1: Al Regression Plot

Figure 2: Ca Regression Plot

Figure 3: Si Regression Plot

Figure 4: Zr Regression Plot